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The pair came together at 56 for four in the 23rd over for New Zealand on the second day of the first test and delivered an antidote to England's bowling venom.
At 236 for five – a lead of 227 - they helped resurrect Black Caps hopes of emulating the feats of their 1999 compatriots to secure a second victory at Lord's in 19 attempts dating to 1931.
Mitchell is 97 and Blundell is 90. They could potentially become the 15th and 16th of their countrymen to score test centuries at the home of cricket.
Their 180-run unbeaten partnership has equalled the New Zealand fifth-wicket record against England, set by Martin Crowe and Shane Thomson at the same venue in 1994.
Mitchell bristled with determination, always looking to heap pressure on the host bowlers who had largely dominated until that point in the test.
He batted out of his crease at times to disrupt length, bruised the ball with regularity and refused to kow-tow to any English lion in cricket's Colosseum.
Blundell entertained with flair, always willing to take a calculated risk against an attack which had dictated the agenda bowling in an off stump channel.
His accentuated movements, whether driving, pulling or leaving, gave the impression he was performing with a bat rather than a cape at La Monumental.
The side's lead is significant.
England has had seven fourth innings chases since February last year, losing five of the matches and drawing two. The most they have compiled is 210.
The historical highest the hosts have scored to win at Lord's was 282 for three in 2004, followed by 218 for three in 1973 – both targets were reached against New Zealand.
The visitors initially struggled to take charge after a dogged recovery to dismiss England for 141 which left them nine runs in arrears.
Will Young was dismissed for one, Kane Williamson 15, Tom Latham 14 and Devon Conway 13; lessons to shore up tentativeness from the first innings showed little sign of correction.
Young was lured forward into an edge by James Anderson, who got the delivery to seam up the slope. Wicketkeeper Ben Foakes launched himself forward to complete the catch as the trajectory faded.
Debutant Matthew Potts removed Williamson for a second time in the match, caught by Jonny Bairstow at third slip. The captain had worked diligently to see off shine, but was tempted into punching a customary back foot drive through mid-off. The bounce from the short-of-a-length ball saw him play loosely and off balance away from his body.
Latham also nicked off to Potts in a corridor outside off stump, but appeared confused whether the back-of-a-length delivery had taken the edge. The decision review system allayed any doubt.
Earlier, the visitors dismissed the hosts for 141 in 42.5 overs after England had resumed on 116 for seven. The world champions demonstrated their capacity to endure and respond to adversity after England's early innings dominance at 59 without loss.
Tim Southee and Trent Boult needed 6.5 overs to wrap up the tail. Southee finished with figures of four for 55 and Boult took three for 21 before Mitchell and Blundell wrested control.
The pair are definitive examples of players developed in the current legacy era who are carrying on the post Cape Town 2013 ethos.
Mitchell, named at number five in place of the injured Henry Nicholls, has long been one of the country's most versatile players.
The 31-year-old has fulfilled multiple roles in his three-year international career; test all-rounder, first-drop against India and No 5 against South Africa in Kane Williamson's absence, and jury-rig opener who guided the side into the Twenty20 World Cup final.
Black Cap number 276 can lay claim to playing consecutive tests twice his first 10 tests. Any disappointment has only driven his will.
Blundell, long touted as the wicketkeeping heir to B-J Watling, has often been the man to seize his opportunities at crucial moments.
Also 31, he became the 11th of the 12 New Zealanders to score a century on test debut in 2017 against the West Indies and – during a period as an opener - he was the first Black Cap to score a test century at the Melbourne Cricket Ground in 2019, albeit in a losing cause.
Black Cap number 273 achieved cult status when he was discovered walking to his Mt Victoria home with a souvenir stump after that victory in his maiden appearance.
Now the pair have the chance to cement further test glory.
- By Andrew Alderson at Lord's